I just bought the VFX impact pack from the marketplace, how do I have the impacts change their particle impacts for different surfaces? I have a line trace for my weapon and a break hit result event after that, how do I make it so that if the player shoots a brick wall the brick wall impact will play and then if they player shoots an enemy that the blood impact will be used. Thanks! 
I think there are several different ways of doing this – you could interrogate the material of the object and based on that you could spawn the correct effect.
Another way might be to create an interface (“IShootable” for example) that accepts a position and a normal as a point at which something was shot. When you hit something, you would attempt to cast it to IShootable, and if this succeeds, you would then send the object an “OnShot” function with the position and normal of the hit (from the trace). Each object that implements IShootable defines its own (different) particle effect, which it would then spawn at the position/normal sent into the OnShot function.
Blueprint Interfaces are described in this video: